BETA-CATENIN EXPRESSION IN HUMAN CANCERS

Cell-cell adhesion in tissue is mainly regulated by homotypic interact ion of cadherin molecules, which are anchored to the cytoskeleton via cytoplasmic proteins, including alpha- and beta-catenin. Although we p reviously demonstrated that alpha-catenin is crucial for cadherin func tion in vivo, little is known about the role of beta-catenin. We exami ned the expression of beta-catenin in human carcinoma samples along wi th normal tissue (esophagus, stomach, and colon) bu immunostaining usi ng our antibody for beta-catenin. Normal epithelium strongly expressed beta-catenin. However, beta-catenin expression was frequently reduced in primary tumors of the esophagus (10 of 15, 67%), stomach (9 of 19, 47%), and colon (11 of 22, 50%). From an immunoprecipitation study, w e found that beta-catenin forms a complex with E-cadherin not only in the normal epithelium but also in cancerous tissues. In coexpression p atterns of E-cadherin and beta-catenin, 43 (77%) of the 56 tumors show ed a similar expression of both molecules, whereas the other 13 tumors (23%) showed positive staining for E-cadherin and reduced expression of beta-catenin. These findings suggest that beta-catenin forms a comp lex with E-cadherin in vivo and down-regulation of beta-catenin expres sion is associated with malignant transformation.